One of the major uses of lithographic systems is in the semiconductor art for manufacturing integrated circuits and the like. Generally, complete semiconductor wafers are processed by forming a large number of similar integrated circuits (semiconductor chips) on the wafer and then cutting the wafer into individual chips. Integrated circuits can be patterned on the wafer in a variety of different ways including optical lithography, X-ray lithography, direct-write electron beam lithography, etc. Optical lithography utilizes masks and reticles which are limited in the minimum feature size that can be achieved and have the additional drawback that each subsequent mask or reticle in the set must be accurately registered with the preceding patterned layer. Also, mask generation, inspection and repair adds substantial cost and time delays, since each step must be done with separate and expensive machinery.
In lithography, the wafer is coated with a photosensitive emulsion and a beam of light (or other energetic particles) passes through the mask or reticle and then exposes the components, circuits, interconnecting lines, etc. in the photosensitive emulsion on the wafer. In the past, for example, it has been found that an X-ray beam can be used to expose lines less than one micron wide. The problem is that it takes a great amount of time to expose all of the features in a plurality of chips with a single X-ray beam. Further, as the size of the wafers increases from 100 mm diameter to as much as 300 mm diameter this problem becomes much greater.
Some multibeam electron lithography systems have been devised but these systems are limited in the size of the wafer which can be written, i.e., because of the means for generating the beam and the focusing utilized, the area that can be exposed simultaneously is limited. Generally only a single type of pattern can be written on the wafer because all of the beams are controlled simultaneously, although the single type of pattern can be written on a number of integrated circuits simultaneously. Also, in many instances it is necessary to provide a different system for each size of the wafer being processed. Further, because of the beam generating means and the focusing elements, the spot size and registration accuracy are limited so that the ultimate resolution is only marginally better than can be produced with other methods.
It would be highly advantageous to provide an electron source for multibeam electron lithography systems which is more controllable and has higher lithographic resolution.
Accordingly, it is an object of the present invention to provide a new and improved electron source with higher resolution than prior art electron sources.
It is yet another object of the present invention to provide a new and improved electron source which can conveniently be used in multibeam electron lithography systems to render these systems much more compliant and versatile.
It is yet another object of the present invention to provide a new and improved electron source which can be utilized on substantially any wafer size and which can be used in an electron beam lithography system to write a variety of different integrated circuit patterns on a single wafer, simultaneously.
It is a further object of the present invention to provide a new and improved electron source which eliminates the need for X-Y scanning deflectors.
It is a still further object of the present invention to provide a new and improved electron source which greatly reduces the current requirements for each individual electron emitter utilized.